Many medical procedures require length measurement of an affected or a diseased portion (such as a stenosis) of a tubular body structure (such as a blood vessel). Such measurements may be performed using quantitative angiography (QA), which uses software processing of acquired images. A known reference length on the image is provided as input to the software, and the operator marks a length of interest. Software processing of the image returns a length measurement. However, QA may not be always accurate due to complex imaging planes, curvature of vessels, and the need for calibration against a known length. Also, QA requires the physician to interrupt the procedure, adding to procedure time, and the software required for QA can be expensive.
An alternative method of length measurement involves the use of a catheter with evenly spaced radiographic markers. Such currently available catheters are ‘over-the-wire’ and can therefore be inconvenient to use in complex interventions. Further, as discussed in an US publication 20030088195 A1, a guide wire having measurement indicia, may address the above issue but this method restricts the physician to a specific type of guide wire. Typically, physicians like to choose guide wires based on their properties and the specifics of a procedure, and do not want to be limited to a particular guide wire that may not be ideal for the procedure. Additionally, markers on the guide wire decrease performance characteristics of the guide wire, and markers on the guide wire may be distracting for other critical parts of the procedure. Given the importance of precise length measurement with millimeter accuracy in many clinical applications, an independent mechanism for confirming (or authenticating) such length measurement is highly desirable.
In light of the foregoing discussion, there exists a need to overcome the aforementioned drawbacks of currently existing methods to measure lengths of tubular body structures in medical procedures.